1. Field of the Invention
The present invention relates to a flame retardant and a flame-retardant resin and/or rubber composition containing said flame retardant. More specifically, it relates to a flame retardant which exhibits excellent flame retardancy when incorporated into a resin or rubber and a flame-retardant resin and/or composition containing said flame retardant.
2. Description of Related Art
The requirement of flame retardancy for a resin and rubber (to be simply referred to as "resin" hereinafter) is getting more stringent year after year. For satisfying this requirement, there is conventionally employed a method in which a so-called halogen-containing flame retardant, typified by a combination of an organic halide and antimony trioxide, is incorporated into a resin. However, the following problems of a halogen-containing flame retardant have come to be recognized. It is liable to generate halogen gas during the processing, and it,corrodes an apparatus, etc. When combusted, it generates a large amount of toxic smoke to threaten human life, and it corrodes peripheral equipment to terminate the function of the equipment.
Aluminum hydroxide and magnesium hydroxide contain no halogen and are free from the above problems. These hydroxides are attracting attention, and the consumption thereof is increasing year after year. Since, however, aluminum hydroxide starts dehydration at about 190.degree. C., it makes almost all resins foam in processing, and deteriorates their product value, The temperature for the processing Is therefore required to be lower than the above temperature, and the resins to which aluminum hydroxide can be incorporated are limited in kind.
Magnesium hydroxide starts dehydration around 340.degree. C., and it can therefore be used with almost all resins without the foaming problem. Further, the present inventor and some other coinventors have invented a magnesium hydroxide suitable as a flame retardant and a process for the production thereof. Magnesium hydroxide is thus beginning to be a mainstream in the field of halogen-free flame retardants. However, for imparting a resin with sufficient flame retardancy, magnesium hydroxide is required to be used in a large amount as well as aluminum hydroxide. For example, the amount of magnesium hydroxide required per 100 parts by weight of a resin is about 150 parts by weight or more. Further, magnesium hydroxide is relatively expensive, and it hence increases the cost much more than a halogen-containing flame retardant. The use of magnesium hydroxide which is a safe flame retardant is not necessarily satisfactorily expanding.